Method and apparatus for opening an end of a braided conductor of a coaxial cable

ABSTRACT

THE APPARATUS INCLUDES AN AIR COMPRESSOR CONNECTED TO A NOZZLE FOR EXPELLING A JET OF AIR THEREFROM. A CLAMPING DEVICE IS SLIDABLY MOUNTED AND HOLDS AN END OF A COAXIAL ELECTRIC CABLE IN ALIGNMENT WITH THE NOZZLE WHICH, IN ONE EMBODIMENT OF THE INVENTION, HAS AN OFFICE SLIGHTLY LARGER THAN THE END OF THE COAXIAL CABLE. A MOTOR-DRIVEN MECHANISM OPERATES TO SLIDE THE CLAMPING DEVICE TOWARD THE NOZZLE FOR BRINGING THE END OF THE CABLE INTO THE JET OF AIR AND, SUBSEQUENTLY, MOVING IT INSIDE THE NOZZLE WHICH, IN ANOTHER EMBODIMENT OF THE INVENTION, HAS A FLARED ORIFICE. THE METHOD COMPRISES THE STEPS OF REMOVING A SECTION OF THE EXTERNAL PROTECTIVE JACKET OF THE COAXIAL CABLE AT AN END THEREOF FOR EXPOSING A PORTION OF THE WOVEN METALLIC WIRES OF THE BRAIDED CONDUCTOR, HOLDING THIS END OF THE CABLE IN ALIGNMENT WITH THE NOZZLE, MOVING THE CABLE END INTO THE JET OF AIR FOR AT LEAST PARTLY UNWEAVING THE BRAIDED WIRES AND THEREBY UNCOVERING A PORTION OF THE UNDERLYING DIELECTRIC MATERIAL, AND THEN INSERTING THE DIELECTRIC MATERIAL INSIDE THE ORIFICE OF THE NOZZLE FOR FURTHER UNWEAVING THE STRANDS OF WIRE AND FOR FORCING THEM TO MOE AWAY FROM THE DIELECTRIC MATERIAL IN A DIRECTION NORMAL THERETO AND THEREBY COMPLETELY OPENING THE END OF THE BRAIDED CONDUCTOR. THE METHOD ALSO COMPRISES THE STEP OF FURTHER INSERTING THE UNWOVEN WIRES BACK OVER THE THE NOZZLE FOR FOLDING THE UNWOVEN WIRES BACK OVER THE EXTERNAL JACKET OF THE CABLE.

NOV. 23, 1971 LE -r 3,621,560

METHOD AND APPARATUS FOH OPENING AN END OF A BRAIDED CONDUCTOR OF A GOAXIAL CABLE Filed July 1'7, 1969 2 Sheets-Sheet 1 DRIVE MECHANISM AIR COMPRESSOR N 8' k I //v I/E/VTOR E. L.L BRIGHT ATTORNEY NOV. 23, 1971 E LE BR|GHT 3,621,560

METHOD AND APPARATUS FOR OPENING AN END OF A BRAIDED CONDUCTOR OF A COAXIAL CABLE Filed July 17, 1969 2 Shams-Sheet 2 United States Patent O US. Cl. 29-427 ll Claim ABSTRACT OF THE DISCLOSURE The apparatus includes an air compressor connected to a nozzle for expelling a jet of air therefrom. A clamping device is slidably mounted and holds an end of a coaxial electric cable in alignment with the nozzle which, in one embodiment of the invention, has an orifice slightly larger than the end of the coaxial cable. A motor-driven mechanism operates to slide the clamping device toward the nozzle for bringing the end of the cable into the jet of air and, subsequently, moving it inside the nozzle which, in another embodiment of the invention, has a flared orifice.

The method comprises the steps of removing a section of the external protective jacket of the coaxial cable at an end thereof for exposing a portion of the woven metallic wires of the braided conductor, holding this end of the cable in alignment with the nozzle, moving the cable end into the jet of air for at least partly unweaving the braided wires and thereby uncovering a portion of the underlying dielectric material, and then inserting the dielectric material inside the orifice of the nozzle for further unweaving the strands of wire and for forcing them to move away from the dielectric material in a direction normal thereto and thereby completely opening the end of the braided conductor. The method also comprises the step of further inserting the entire end of the cable inside the nozzle for folding the unwoven wires back over the external jacket of the cable.

GOVERNMENT CONTRACT The invention herein claimed was made in the course of, or under contract with the Department of the Army.

BACKGROUND OF THE INVENTION This invention relates to a method and apparatus for opening an end of a woven cylinder, and, more particularly, to a method and apparatus for opening an end of a braided cylindrical conductor of a coaxial electric cable.

Various types of equipment employ woven or braided cylinders which are used for performing a number of different functions. For example, one form of a coaxial electric cable comprises an inner central conductor covered with dielectric material which is surrounded by a braided outer conductor consisting of metallic wires woven together in cylindrical form about the dielectric material so as to be concentrically positioned with respect to the central conductor. In addition, the braided conductor, which performs an electric shielding function, is usually covered with a suitable external protective jacket.

There are occasions when it becomes necessary to open an end of a Woven or braided cylinder in order to perform certain operations. In the case of a coaxial cable, an end of its braided conductor must be opened whenever the cable is to be connected or attached to some other piece of electric equipment, such as a coaxial coupling device.

In order to perform a coaxial connection of this type, the ends of the two coaxial conductors in the cable must first be bared or uncovered so that other electrically conductive devices can be fastened to them. Accordingly, it is necessary that a section of the external protective jacket adjoining the end of the cable be removed or stripped away for exposing a portion of the braided conductor at this end of the cable. Next, this exposed portion of the braided cylindrical conductor must be opened to uncover the underlying section of dielectric material. The uncovered dielectric material must then be stripped off so as to bare a portion of the central coaxial conductor. This procedure results in exposing the end portions of the two coaxial conductors thereby rendering them available for making connections to a coaxial coupling device or to some other form of electric equipment.

Usually, no problems are encountered in removing sections of the external protective jacket and the dielectric material because various stripping tools and equipment are available for this purpose. However, considerable difliculty has been experienced in attempting to open quickly an end of the braided cylindrical conductor. This is due to the fact that, since the metallic wires are woven together, they naturally tend to bind against each other and thus resist opening.

Heretofore, one method of opening an end of a braided cylindrical conductor has employed the step of manually combing the braided wires in order to unweave them. This must be done carefully so as not to break the individual strands of wire. Care must also be exercised in order to prevent the wires from flaking with the consequent hazard of some of the flakes becoming embedded in that portion of the underlying dielectric material which is not stripped away. It has been shown by time-cost studies that, for one type of coaxial cable, the opening of one end of its braided conductor requires a manual combing operation having a duration of three and one-half minutes. Accordingly, it can be understood that, any project which employs this manual combing procedure for opening the ends of a large number of braided conductors will consume a considerable amount of time and will therefore be expensive.

SUMMARY OF THE INVENTION The present invention is designed to provide an improved method and apparatus for quickly and efficiently opening an end of a woven or braided cylinder, such as the braided cylindrical conductor of a coaxial electric cable. The apparatus includes a nozzle having an orifice which, when used with a coaxial cable, is at least slightly larger than the end of the cable. In one embodiment of the invention wherein, after the end of the braided conductor has been at least partly opened, it is desired to fold the unwoven wires back over the external protective covering of the cable, the orifice is flared. An air compressor is connected to the nozzle for expelling a jet of air from the orifice with sufficient force to at least partly unweave the metallic wires in the braided cylinder. A clamping device is slidably mounted for holding an end of the cable in alignment with the nozzle. A motor-driven mechanism functions for sliding the clamping device toward the nozzle for bringing the end of the cable into the jet of air and, subsequently, moving it inside the orifice.

When this apparatus is employed for opening an end of a braided conductor of a coaxial cable, the method of this invention comprises the steps of removing a section of the external protective jacket of the cable for exposing a portion of the woven metallic wires constituting the braided conductor, holding this end of the cable in alignment with the nozzle, moving the cable end into the jet of air for at least partly unweaving the braided wires and thereby uncovering a portion of the underlying dielectric material, and then inserting the dielectric material into the nozzle for further unweawing the strands of wire and for forcing them to move away from the dielectric material in a direction normal thereto thereby completely opening the end of the braided conductor. The method also comprises the step of further inserting the entire end of the cable inside the nozzle for folding the unwoven wires back over the external jacket of the cable. Thus, the method of this invention greatly reduces the time required for opening the end of the braided conductor.

BRIEF DESCRIPTION OF THE DRAWING The features of this invention are more fully discussed hereinafter in connection with the following detailed description of the drawing in which:

FIG. 1 is a perspective view of a coaxial electric cable having portions removed at one end thereof for the purpose of showing its components;

FIG. 2 is a schematic side view of a portion of a machine for practicing the method of this invention on a coaxial electric cable having a braided cylindrical conductor;

FIG. 3 is a side view, partly in section, of the machine shown in FIG. 2 and, in addition, illustrating the method of applying a jet of air for opening an end of the braided cylindrical conductor of a coaxial electric cable;

FIG. 4 is a side view somewhat similar to FIG. 3 but showing a different nozzle having a flared opening with a portion of the cable inserted therein for folding the unwoven wires back over the external protective covering of the cable;

FIG. 5 is a side view somewhat similar to a portion of FIG. 4 but also showing cutting blades for cutting and stripping an end portion of the dielectric material on the cable;

FIG. 6 is a side view of an end of the cable with an end portion of its central conductor bared and having an end of its braided conductor unwoven and folded back over the outer covering on the cable;

FIG. 7 is a side view somewhat smilar to FIG. 6 but, in addition, having a coaxial coupling device connected to the concentric conductors of the coaxial cable;

FIG. 8 is a sectional side view of an end of the cable with an end portion of its central conductor bared and having the end of the braided conductor unwoven and raised away from the dielectric material for exposing a section thereof; and

FIG. 9 is another sectional side view of the end of the cable shown in FIG. 8 but includes the addition of a coaxial coupling device which is different from the coaxial coupler shown in FIG. 7.

DETAILED DESCRIPTION The method and apparatus for opening an end of a woven cylinder in accordance with this invention will now be described with reference to a specific exemplary embodiment thereof; namely, a machine for performing a mechanical method of opening an end of a braided cylindrical conductor of a coaxial electric cable. A coaxial electric cable of the type used with this invention is shown in 'FIG. 1 wherein it an be seen that the cable 1 comprises an inner central conductor 2 which is in the form of a solid metallic wire. This inner conductor 2 is covered with a coating of a suitable dielectric material 3 which is surrounded by a braided outer conductor 4 composed of a number of metallic wires. These wires are woven together in the form of the cylinder about the dielectric material 3 and are so disposed as to be concentrically positioned with respect to the inner conductor 2. The braided conductor 4 is, in turn, covered with an externalprotective jacket 5. The braided conductor 4 performs an electric shielding function and the external jacket 5- protects the braided conductor 4 from becoming rubbed or scraped.

When it is desired to connect the end of the coaxial cable 1 to other electric equipment, it is usually necessary to connect the end of the cable 1 to a coaxial coupling device which is suitably designed to prevent the formation of an impedance discontinuity. Such a coaxial coupling device ordinarily includes one member which is designed for connection to the inner coaxial conductor 2 and another member which is adapted to be fastened to the outer coaxial braided conductor 4. In order for these members of the coaxial coupling device to be joined to the coaxial conductors 2 and 4, it is first necessary to remove portions of the dielectric material 3 and the external jacket 5 in order to bare or expose the end sections of the coaxial conductors 2 and 4.

As was stated above, various stripping tools and equipment are available for removing portions of the dielectric material 3 and the external jacket 5, but, heretofore, there has been no satisfactory method of quickly opening the end of the braided conductor 4. However, in accordance with the method and apparatus of this invention, the end of the braided conductor 4 can be quickly and efficiently opened as will now be explained with reference firstly to FIG. 2 which is a schematic illustration of a machine for practicing the method of this invention.

In FIG. 2, a conventional air compressor 6 is adapted to provide a supply of compressed air via a suitable tube 7 to a block 8 having a passage 9 therethrough. The block 8 is mounted on a supporting rod 10' and has a threaded opening 11 at one end for receiving the threaded end of a nozzle 12 inserted therein. This nozzle 12 has an orifice 13 from which a jet of air is expelled as is indicated by the arrows issuing therefrom. In this embodiment of the invention, the orifice 13 is made slightly larger than the end of the cable 1.

Directly opposite the orifice 13, an end of the coaxial cable 1 is fastened to the upper portion of a holding rod 14 by means of a suitable clamping device 15'. Thus, the clamping device 15 and the rod 14 function as means for securely holding an end of the cable 1 in alignment with the nozzle 12. It can be seen that, on the cable 1, a section of the external protective jacket 5 adjoining the end of the braided conduct-or 4 has been removed in order to expose a portion of the woven metallic wires 4 which are normally covered by the jacket 5. The removal of this section of the external jacket 5 is accomplished in any appropriate manner known to those skilled in the art, such as by using suitable stripping equipment.

The holding rod 14 is slidably mounted on a guide rod 16 which is securely attached to the supporting rod 10 by means of a clamp 17. This serves to slidably connect the holding rod 14 to the supporting rod 10. The sliding movement of the rod 14 back and forth along the guide rod 16 is accomplished by rotating a lead screw 18 which is threaded through the lower end of the rod 14. This lead screw 18 is adapted to be rotated alternatively in either a clockwise direction or a counterclockwise direction by means of a suitable drive mechanism 19. Thus, the rotation of the lead screw 18 will cause the end of the cable 1 to move in a reciprocating manner; that is, it will be either advanced toward the orifice 13 or retracted therefrom as is indicated by the double ended arrow drawn under the end of the cable 1.

From the above description, it can be understood that the first step of the method of this invention involves removing a section of the external jacket 5 adjoining the end of the braided conductor 4. The second step consists of employing means, comprising the clampingdevice 15 and the rod 14, for securely holding the end of the cable 1 in alignment with the orifice 13 of the nozzle 12.

The next portion of the method comprises moving the end of the cable 1 into the jet of air issuing from the orifice 13 of the nozzle 12. This portion of the method is performed by actuating the drive mechanism 19 for rotating the lead screw 18 and thereby effecting sliding movement of the holding rod 14 along the guide rod 16 in a direction toward the nozzle 12 as is indicated by the arrow in FIG. 3.

When the end of the cable 1 is moved close to the nozzle 12, it receives the force of the jet of. air issuing from the orifice 13. Since the air compressor 6 is designed to expel the jet of air from the orifice 13 with sufiicient force to at least partly unweave the braided conductor 4, the individual strands of wire will begin to become separated from each other as is represented in FIG. 3. The effect of the jet of air is increased by moving the end of the cable 1 into juxtaposition with the orifice 13 with the result that the strands of wire in the uncovered portion of the braided conductor 4 become completely unwoven and are blown away from the end of. the dielectric material 3 thereby opening the end of the braided conductor 4 and exposing an end section of the dielectric material 3.

If it is desired to open the end of the braided conductor 4 to a greater extent, this can be accomplished by causing the lead screw 18 to move the cable 1 closer to the nozzle 12 so as to insert the exposed end of the dielectric material 3 inside the orifice 13. This causes the force of the jet of air to become more concentrated so that it forces the unwoven metallic wires to move away from the dielectric material 3 in a direction normal thereto thereby completely opening the uncovered portion of the braided conductor 4.

For certain types of coaxial coupling devices, it is required that the unwoven wires of. the outer conductor 4 be bent or folded back over the external protective jacket 5 of the cable 1. This operation can be performed by causing the end of the cable 1 to be fully inserted inside the nozzle as is shown in FIG. 4. In performing this phase of the method of this invention, it is preferable to employ a slightly different nozzle 12' having a flared orifice 13. The insertion of the end of the cable 1 inside the nozzle 12 serves to concentrate the force of the jet of air to a greater extent thereby causing the unwoven wires to bend backward in a direction away from the orifice 13'. As the end of the cable 1 moves inside the nozzle 12', the flared shape of the orifice 13 causes the wire strands 4 to become bent further backward until they are completely folded back over the external jacket 5 thereby fully exposing a section of the dielectric material 3.

The lead screw 18 is now rotated in the opposite direction for causing the holding rod 14 to move to the right in the drawing thereby retracting the end of the cable 1 from the orifice 13'. The end of the cable 1 is thus moved to a predetermined position where, as is shown in FIG. 5, the exposed section of the dielectric material 3 is posi tioned between two cutting blades 20 and 21 which are adapted for reciprocating motion toward and away from the dielectric material 3. It is to be understood that these cutting blades 20 and 21 are actually included in the apparatus shown in FIGS. 2, 3, and 4 but have been omitted therefrom for the purpose of obtaining simplicity in the drawing.

The cutting edge of each of the blades 20 and 21 is semicircular so that each can cut one-half of the crosssectional area of the dielectric material 3 without cutting the center conductor 2. The apparatus is so designed. that, during the reciprocating movement of the blades 20 and 21, they never come so close together as to cut the center conductor 2. When the blades 20 and 21 are moved toward each other for piercing the dielectric material 3, they remain in this position for a brief. interval of time. During this period, the end of the cable 1 is retracted further toward the right thereby stripping or removing from the cable 1 that portion of the dielectric material 3 which is at the left of the blades 20 and 21. As a result, the end of the inner coaxial conductor 2 is bared.

This procedure leaves the end of the cable 1 in the condition shown in FIG. 6 wherein it can be seen that the bared inner conductor 2 protrudes at the left end of the cable 1. Also, a short section of the dielectric material 3 is exposed due to the fact that the unwoven strands of. wire of the other coaxial conductor 4 are now folded back over the external protective jacket 5. Accordingly,

this end of the cable 1 is now in condition for being joined to a coaxial coupling device.

The mating of this end of the cable 1 with a coaxial coupler 22 is illustrated in FIG. 7. The coaxial coupler 22 comprises an outer tubular member 23 of electrically conductive material into which the end of the cable 1 is inserted so that the outer tubular member 23 is pushed over the portion of the unwoven wires 4 that are completely folded back over the external protective jacket 5 thereby enclosing the wires 4 within the outer tubular member 23. The coaxial coupler 22 further includes an inner tubular member 24 which is also made of electrically conductive material. At the same time that the outer tubular member 23 is pushed over the folded wires 4, the inner member 24 is pushed over the bared end of the inner coaxial conductor 2 until it abuts against the end of the uncovered portion of the dielectric material 3. The space between the inner and outer members 24 and 23 is filled with a suitable dielectric material 25. The outer member 23 is securely fastened to the wires 4 in any suitable manner, such as by crimping or soldering. Similarly, the inner member 24 is securely fastened to the inner coaxial conductor 2. Thus, the end of the cable 1 is joined to the coaxial coupling device 22 which leads to some other piece of electric equipment.

If it is desired to use a different type of coaxial coupling device, such as the coaxial coupler 26 shown in FIG. 9, then it is not necessary to employ the method step of folding back the wires 4 as is represented in FIG. 4. Instead, the process step indicated in FIG. 3 is continued until the wires in the uncovered portion of the braided conductor 4 are unwoven and are blown outward to expose the dielectric material 3. A section of this exposed dielectric material 3 is now stripped away by any suitable means, such as those represented in FIG. 5. This serves to bare a short portion of the inner coaxial conductor 2. The end of the cable 1 will now have the appearance illustrated in FIG. 8.

The coaxial coupling device 26 that is shown in FIG. 9 comprises an inner tubular member 27 of electrically conductive material which is pushed over the bared inner coaxial conductor 2 until it abuts against the end of the dielectric material 3. The coupler 26 further includes a tubular member 28 of electrically conductive material which is pushed over the uncovered portion of the dielectric material 3 and underneath the unwoven wires 4. The space between the tubular member 28 and the inner member 27 is filled with a suitable dielectric material 29. Next, a ferrule 30, which has been previously placed over the end of the cable 1, is now moved to the left to flatten the unwoven wires 4 as is indicated in FIG. 9. The ferrule 30 is then fastened in place by any suitable means, such as by crimping. This results in the unwoven wires 4 being compressed between the tubular member 28 and the ferrule 30 thereby completing the joining of the end of the cable 1 to the coaxial coupler 26.

I claim:

1. A method for attaching an end of a coaxial coupling device to an end of a coaxial electric cable,

said coaxial electric cable comprising a central electric conductor covered with dielectric material,

a braided conductor consisting of a multiplicity of metallic wires woven together in cylindrical form about said dielectric material and concentrically positioned with respect to said central conductor,

and an external protective jacket covering said braided conductor,

said coaxial coupling device comprising an inner tubular member positioned within an outer tubular member and sparated therefrom by dielectric material,

said method comprising the steps of removing a section of said external jacket adjoining said end of said coaxial cable for exposing an end portion of said woven wires normally covered thereby,

holding said exposed end portion of said braided conductor in alignment with a nozzle having an orifice with a jet of air issuing therefrom,

moving said exposed portion of said braided conductor into said jet of air for at least partly unweaving said wires in said exposed portion,

additionally moving said exposed portion of said braided conductor into juxtaposition with said orifice for further unweaving said wires in said exposed end portion of said braided conductor and for at least partly uncovering an end portion of said underlying dielectric material,

inserting said partly uncovered end portion of said dielectric material into said orifice for concentrating the force of said jet of air for completely unweaving said wires in said exposed end portion of said braided conductor and for forcing said wires to move away from said dielectric material in a direction normal thereto and for thereby completely uncovering said end portion of said dielectric material,

inserting the entire end of said coaxial cable together with said unwoven wires inside said nozzle for further concentrating the force of said jet of air and for folding said unwoven wires completely back over said external protective jacket,

removing at least some of said dielectric material in said uncovered end portion for thereby baring an end portion of said central electric conductor,

pushing an end of said inner tubular member of said coaxial coupling device over said bared end portion of said central electric conductor until said inner tubular member abuts against the end of said uncovered portion of said dielectric material,

simultaneously pushing an end of said outer tubular member of said coaxial coupling device over the portion of said unwoven wires that is completely folded back over said external protective jacket for thereby enclosing said folded wires within said end of said outer tubular member,

and securely fastening said end of said outer tubular member to said enclosed folded wires.

References Cited UNITED STATES PATENTS 8/1966 Bilco 81-9.5l 3/1970 Jasberg 156-584 JOHN F. CAMPBELL, Primary Examiner D. P. ROONEY, Assistant Examiner 

